Advocate Illinois Masonic Medical Center

Surgery Air-Handling Unit Replacement and Pressurization Upgrade, Design

Surgery Air-Handling Unit Replacement and Pressurization Upgrade, Design - Chicago, IL


The hospital retained GBA to design a crucial replacement to two primary surgery air handlers and related equipment. 


The 1.14 million-square-foot hospital on Chicago’s North Side required upgrades to ventilation for a surgical unit. GBA designed the replacement of two primary surgery air handlers and corresponding exhaust fans serving the third-floor surgical suite (12 operating rooms and a post-anasthesia care unit).

  • The new AHUs are custom, hospital-grade units of about 30,000 cfm each, using fan array technology.
  • A heat recovery system, consisting of a glycol loop and coils, transfers energy from the exhaust airstream to preheat or pre-cool the outside air introduced.
  • GBA field-verified existing conditions and devised upgrades with a phasing plan to keep interruptions to a minimum. Temporary connections were provided to maintain airflow in areas served by the existing AHUs, ensuring continuous service to all ORs. Work was closely coordinated with the hospital and OR staff.
  • Some air terminals were added and others were upgraded to DDC to ensure that correct air changes and pressurization are maintained throughout the surgical suite. 
  • Operating rooms were tested for air tightness, and architectural measures (sweeps, astragals, and miscellaneous joint sealing) were implemetned to reduce the airflow offset required to maintain room pressurization. Ductwork was cleaned, and portions were sealed to reduce leakage.
  • GBA provided commissioning services to ensure that pressurization was appropriate after the new equipment was installed.